Radiation detector apparatus



Sept. 12, 1961 A. TAYLOR RADIATION DETECTOR APPARATUS Filed NOV. 29,1939 TO AMPLIFIER) AMPLIFIER TO BALHNCIN NET WORK 2,999,934 RADIATIONDETECTOR APPARATUS Laurens A. Taylor, Schenectady, N.Y., assignor, bymesne assignments, to the United States of America as represented by theSecretary of War Filed Nov. 29, 1939, Ser. No. 306,755 7 Claims. (Cl.250-833) This invention relates to thermo-responsive devices forlocating distant objects by therma -radiation and it con-' stitutes afurther development of the apparatus for detecting distant objects byheat radiation described and claimed in the copending application ofCharles F. Green, filed November 29, 1939, Serial No. 306,753.

One object of this invention is to provide a thermoresponsive detectoradapted to be used in connection withcollector-thermo-couple-amplifier-indicator systems, which willmaterially facilitate the detection of distant objects by said systems,owing to its simplicity and rapidity in response and angle of pickup.

Another object of this invention is to provide a thermoresponsivedetecting device of the character specified having a plurality ofthermo-couple strips arranged and proportioned so that said device whenused with a suitably dimensioned reflector will afford a wide verticalacceptance angle or spread, particularly useful in systematic searchingfor unseen targets.

Another object of this invention is to provide a detecting apparatusequipped with a thermo-responsive device in the nature of an evacuatedtube provided with a window having a high transmission coeflicient andcontaining a pair of suitably disposed thermo-couple strips, in-

teroonnected within the tube to afford bucking out-' puts, therespective length of the strips being such as to provide a verticalacceptance angle, suitable for systematic searching.

Another object of this invention is to provide a detecting apparatus,including a thermo-responsive detector in the nature of an evacuatedtube having a rock-salt window and containing a pair of horizontaldisposed thermocouple strips folded within the tube to provide therequisite spacing for their vertically extending junction lines.

With these and other objects in view, this invention consists in certainnovel details ofconstruction, combination and arrangement of parts to bemore particularly hereinafter described and claimed.

Referring more particularly to the accompanying drawings in which partsare designated by similar reference characters:

FIG. 1 is a sectionized diagrammatic view of acollector-thermo-couple-amplifier-indicator system illustrating oneembodiment of the instant invention; 7

FIG. 2 is a sectionized perspective'view of the thermoresponsivedetecting device adapted to be used in connection with the apparatusshown in FIG. 1, and illustrating the arrangement, mounting andconnections of the thermo-couple strips within the tube;

FIG. 3 is a fragmentary detailed perspective of the therrno-cou-plestrips within the detector tube; and

FIG. 4 is a perspective view of a modification of thermo-couple stripsshown in FIGS. 2 and 3.

In the form of thermo-couple as described and claimed in the applicationof Charles F. Green, filed November 29, 1939, Serial No. 306,753, thejunction strips are mounted side by side and connected in such a mannerthat their outputs are in bucking relation. While useful in backgroundinvestigations, determination and com-- parison of ranges andcharacteristics of systems, this type of thermo-couple tube, owing toits limited pickup anand azimuth may be effected for the purpose ofpointing gle is not suited to systematic searching for distant tar-. 7

gets. It is therefore the aim and purpose of the instant Patented Sept.1-2, 1961 invenion to provide a line thermo-couple tube having itsthermo-couple strips arranged and proportioned to provide a pickup anglewhich will greatly facilitate systematic searching.

In .the illustrated embodiment characterizing this invention a drum 1 ispivotally mounted at -2 betweenthe arms of a yoke 3 which is swivellysupported on base 4., This arrangement permits vertical andhorizontaloscillwtion of the drum as clearly shown in FIG. 1 ofthe'drawings. Suitable means are provided for moving. the drum in eachof the two planes whereby changes in elevation the drum. While suchmeans maybe manualor power operated, the former is illustrated for thesake of simplicity; thus, the handwheel Soperates through the worm 6 andworm-wheel 7 .to move the drum in the vertical plane and the handwheel 8functions through worm 9 and worm-wheel 10 to move the drum in thehorizontal plane.

Within the drum is mounted the reflector 12 in the focal region of whichis arranged a line thermo-couple tube 13, the tube'being suitablysupported on the upper end of a standard 14 as shown in FIG. 1 of thedrawings. This device comprises two thermo-couple, strips 15 and 16,which are in the present instance horizontally disposed and arranged inend to end relationwith the junction lines 20 extending vertically, asclearly shown in FIG. 2 of the drawings. V

The thermo-couple strips 15 and 16 are mounted within and near one endof an evacuated envelope 17. This envelope comprises a glass portion 18having a metallic end portion 19, which in the present instance is asilver sleeve and a window or end plate 21 having a high trans; missioncoefficient, such as rock-salt. The "sleeve has a thin tapered edge atboth ends, the glass being fused over the inner end, and the outer endof the sleeveis made vacuum tight with the rock-salt window by asuitable seal such as silver chloride, which constructionis describedand claimed in the copending application of August J. Kling, filedNovember 29, 1939, Serial No. 306,750, now Patent No. 2,593,369.

Each of the thermo-couple strips '15 and 16 is composed of twothermo-electrically dissimilar metals welded together along the junctionline 20. These thermo-' couple strips have been made by welding togetherthin plates of the desired material at their edges and then rolling downthe welded plates until they obtain the desired thinness, which is ofthe order of 6 to 10 millionths of an inch. Since the direction of therolling is transversely of the strip, or in other words, in thedirection of the junction line 20, the welded connection between the twometals is preserved even though the thickness of the resulting strip isreduced to a few millionths of an inch. Very successful results havebeen obtained by employing for one element of the thermo-couple strip analloy composed of nickel 44%, copper 55.5% and iron 0.5%, commonly knownas Copnic, and for the other element of the thermo-couple strip an alloycomposed of nickel and chromium 10%, commonly known as Chromel."

Assuming that the apparatus is to be used for horizontal searching, thatis, the drum and reflector are to be swung in azimuth at a givenelevation, the two thermocouple strips 15 and 16 as previously statedare arranged horizontally in an end to end relation with the junctionlines 20 extending vertically. The two junctions are connected in seriesand in a reverse manner, the two outer elements, which are of onepolarity being secured to support bars 25 and 26, and the two inner orinter-' mediate elements which are of the'opposite polarity beingsecured to the intermediate bar 23.

With this type of thermo-couple strip the lengthof;

eachjunction line 20 is from three to seven times the length of thejunction line disclosed in the thermo-couple strips described andclaimed in the hereinabove mentioned application of Charles F. Green.The width of each junction is therefore many times the diameter of theimage represented, for example, by the dotted circle 21a of theradiating body. The lengths of the electrically dissimilar metalsforming each thermo-couple strip are substantially equal, the exactlengths being such that the rates of heat conduction to the supportingbars, considering the heat conducting properties of the materials, areequal. The intermediatebar 23 is approximately twice the size of each ofthe outer bars 25 and 26, whereby it has approximately twice the heatcapacity thereof. The junction line 20' is substantially in the middleof each strip, but in order to bring the two junction lines closertogether the inner elements 15a- 16a of the thermo-couple strips 15 and16 are bent backward as shown in FIGS. 2, 3 and 4. By thus bringing thetwo junction lines 20 closer together, one junction can be made torespond to a background regionof radiation which is closer to the bodywhose radiation effects the other junction. By connecting thethermo-couple strips so that they oppose each other, in so far asbackground radiation is concerned, the one thermo-junction will exactlybalance the other and no indication will be given by the indicatingmeter, hereinafter to be referred to.

The two thermo-couple strips are mounted with the outer elements as wellas the adjacent portions of the inner elements in the focal region ofthe reflector and are horizontally offset so that the focal point of thereilector falls on one junction line 20 at approximately the middlethereof. As shown in FIGS. 2 and 3, the inner bar 23 is connected to andsupported by the wire 24 which extends through the stem of the tube tothe exterior thereof and is connected to terminal 24a of the terminalblock A. The outer bars 25 and 26 are affixed to and supported by thewires 27 and 28 which extend through the stem of the tube, as clearlyshown in FIG. 2, and are connected to terminals 27a and 28a of terminalblock A. These terminals 27a and 28:: are connected via conductors27b'--2S'b with the input side of an amplifier 31. The output side ofamplifier 31 is connected through suitable conductors to a rnilliammeterindicator 32, as shown in FIG. 2 of the drawings.

To correct for small differences in resistance in thermojunction thatmay occur in manufacture, a balancing network (not shown) may beconnected via conductors 24b-27c between terminals 27a--24a, whereby thetwo thermo-couple strips may have equal resistances when exposed toequal amounts of radiation, thus retaining the pointer of the indicatorat zero.

The form of thermo-couple strip which is shown in FIGS. 2 and 3, andwhich is relatively wide, giving a relative long junction line 20 isequivalent to a number of narrower thermo-couple strips connected inparallel. In certain cases it may be desirable to employ a number ofnarrow thermo-couple strips and connect them in series relation. Such anarrangement is shown in FIG. 4, in which several narrow thermo-coupl'estrips 1512-1611 are supported by separate bars of which adjacent barsof one polarity are mounted upon the insulating supports 27d, as clearlyshown in FIG. 4 of the drawings. The thermo-junction strips are suitablyconnected in series by the conductors 29a29b. It has been found that forthermo-couple strips constructed of the same materials and having thesame area, series or parallel connections will give equal power output,provided the load resistance is matched to the thenno-junction.

In conclusion, it will be seen that this invention presents a detectingapparatus, embodying a high vacuum line thermo-couple tube havingarock-salt window and containing a pair of thermo-couple junctionstrips, connecte'd'in bucking? relation and folded in a manner to spacethe vertically extending junction lines, a distance which experience hasdemonstrated gives the most effective results, and that when this tubeis mounted in the focal region of a suitably dimensioned reflector, andconnected to an amplifier-indicator system, as shown in FIG. 1, there isprovided at detecting apparatus which is sensitive over a long range,rapid in response and efficient in searching for unseen targets, owingto it's relatively wide angle of pickup.

Having described my invention, what I claim as new and wish to secure byLetters Patent is:

1. In an apparatus for locating distant bodies by thermo-radiation,means for collecting: and focusing the heat radiation from a distantbodyto form a thermal image thereof, means 'within the focal region. ofthe collected heat radiation for translating thermal intoelectricalenergy, said means including an evacuated vessel provided with arock-salt window, ther-mo-responsive means within the vessel, said meansbeing electrically connected in opposition to effect automaticcompensation for changes in background radiation and' including a pairof vertically extending laterally spaced thermal mal image formed bysaid first-mentioned means and an indicating device in electricalrelation with said thermo-responsive means.

2. In an apparatus for locating distant bodies by thermo-radiation,means for collecting and focusing the heat radiation from a distant bodyto form a-thermal image thereof, means within the focal region of thecollected heat radiation for translating thermal into electrical energy,said' means including an evacuated vessel provided with a rock-saltwindow, thermo-responsive means within the vessel, said means includinga pair of ther'rno-couple strips arranged-in end to end relation andelectrically connected in opposition to effect automatic compensationfor changes in background radiation, each of said strips including athermal junction line extending transversely of its lengthand'coextensive with-its width, the length of said coextensive linebeing such as to afford a relativelywide'vertical acceptance angle, oneof said thermal junction lines being positioned to receive the thermalimage formed by said first-mentioned means and an electro-r'esponsiveindicator in electrical relation with the thermo-couple strips.

3. In an' apparatus for locating distant bodies by thermo-radiation,means for collecting and focusing heat radiation from a distant body toform a thermal image thereof, means within the'focal region of thecollected heat radiation for translating thermal into electrical energy,said means including an evacuated vessel provided tion lines beingdisposed to receive the thermal image formed by said first-mentionedmeans, and an electric responsive indicator in electrical relation withthermocouple strips.

4. 'In an apparatus for locating distant bodies'by thermoradiation,means for collecting and focusing the'heat radiation from a distant bodyto form a thermal image thereof, means within the focal region of thecollected heat radiation for translating thermal into electrical energy,said means including an evacuated vessel provided with a rock-saltwindow, thermo -responsive means within the vessel, said means embodyinga pair' ofthermo couple strips of a predetermined order of" thinnessarranged in end to end relation andelectrically connected in. oppositionto efiect automatic compensation forchanges in background radiation,each of said strips embodying a vertically disposed thermo-junction linecoextensive with the width of the strip, the thermo-junction lines ofthe two strips being parallel and laterally spaced a predetermineddistance, the length of said thermal junction lines being such as toafford a Wide vertical acceptance angle, one of said thermal junctionlines being disposed to receive the thermal image formed by saidfirst-mentioned means, and an electro-responsive indicator in electricalrelation to the thermo-couple strips.

5. In an apparatus for locating distant bodies by thermo-radiation,means for collecting and focusing the heat radiation from a distant bodyto form a thermal image thereof, means Within the focal region of thecollective heat radiation for translating thermal into electricalenergy, said means including an evacuated vessel provided with arock-salt window, thermo-responsive means within the vessel, said meansincluding a pair of thermocouple strips arranged in end to end relation,each strip being composed of electrically dissimilar alloys of apredetermined order of thinness united along a vertically disposedjunction line coextensive with the width of the strip, said strips beingelectrically connected in opposition for effecting automaticcompensation for changes in background radiation, one of said thermaljunction lines being disposed to receive the thermal image formed bysaid first-mentioned means, the length of the re spective junction linesbeing such as to afiord a wide vertical acceptance angle, and anelectro-responsive indicator in electrical relation with thethermo-couple strips.

6. In an apparatus for locating distant bodies by thermo-radiation,means for collecting and focusing heat radiation from a distant body toform a thermal image thereof, means within the focal region of thecollected heat radiation for translating thermal into electrical energy,said means including an evacuated vessel provided with a rock-saltwindow, thermo-responsive means within the vessel, said means comprisinga pair of thermocouple strips arranged in end to end relation andelectrically connected in opposition to eflfect automatic compensationfor changes in background radiation, each of said strips being of apredetermined order of thinness and including a vertically disposedjunction line coextensive with the width of the strip, the thermaljunction line of one of said strips being disposed to receive thethermal image formed by said first-mentioned means, said strips beingfolded rearwardly within the tube to juxtaposition the junction lines,and an electro-responsive indicator in electrical relation with saidthermo-couple strips.

7. In an apparatus for locating distant bodies by thermo-radiation,means for collecting and focusing heat radiation from a distant body toform a thermal image thereof, means Within the focal region of thecollected heat radiation for translating thermal into electrical energy,said means including an evacuated vessel having a window transparent tothermal radiation, a plurality of thermo-couple strips Within the vesseland immediately to the rear of the window, said strips being arranged inend to end relation and electrically connected in opposition to effectautomatic compensation for changes in background radiation, one of saidthermal junction lines being disposed to receive the thermal imageformed by said first-mentioned means, said strips being of apredetermined order of thinness and including parallel laterally spacedjunction lines, the length of said lines being such as to afford a Widevertical acceptance angle, and an electro-responsive indicator inelectrical relation with said thermo-couple strips.

References Cited in the file of this patent UNITED STATES PATENTS1,343,393 Hoflman June 15, 1920 1,963,185 Wilson June 19, 1934 1,971,317Sheldon Aug. 21, 1934 2,015,675 Hays Oct. 1, 1935 2,125,113 Kling July26, 1938 2,144,519 Wilson Ian. 17, 1939

